Aquatic plants commonly arise as undesired weeds in waters and wetlands. Three such weeds are hydrilla, curlyleaf pondweed, and watermilfoil, including Eurasian watermilfoil. The treatment of bodies of water to eliminate or control the undesired aquatic weeds is often complicated by the fact that the agent used to control the undesired weed may also adversely affect the health of desirable or native plant life. Aquatic herbicides need to be in contact with aquatic (submersed, immersed or floating) plants for a period of time to be effective. Some herbicides require long exposures (one or more months) to control certain submersed, immersed, or floating plants in water, which can adversely affect non-target plant species. Long exposure times can be difficult to achieve in a fluid environment. Insufficient exposure can lead to poor efficacy or failed treatments. Thus, methods or techniques to reduce exposure times and/or reduce the concentrations of agents used to control aquatic weeds may benefit efficacy and/or selectivity.
The efficacy of herbicidal agents against the target aquatic weeds depends on multiple factors, including but not limited to the application dose, the active ingredient, the specific formulation, the plant type, plant susceptibility, climatic conditions, water and sediment conditions, and herbicide exposure time. At times, an inability to control an undesired aquatic weed can be overcome simply by increasing the application rate or concentration of a particular herbicidal agent. However, this is not always the case, and higher application rates can cause adverse or undesired effects on beneficial aquatic plants and aquatic organisms and may not adequately compensate for rates necessary to control the targeted aquatic plant.